Re: MCH0602 Boundary alignment error -- RPG400-L

Hi there,

When I run the caller program, I'm gettting the MCH0602 error.  I was
under the impression that I do not need to recompile caller program as
long as the change that I made to the service program doesn't cause the
signature to change.  Is that a wrong assumption?

Yes, it's a wrong assumption. Service program signatures are merely ahash taken over the list of exported items. They don't track whether youmake changes to parameters or return values. All they keep track of isthe export names.

Therefore it's completely possible (as you've discovered) to breakbackward compatibility without changing the signature.

My suggestion to you is that you don't break backward compatibility.Don't change the sizes or data types of existing parameters or returnvalues. If you have additional parameters to add, always add them at theend, and use options(*NOPASS) and code your procedure so that it doesn'trequire the newly added parameter.

If you MUST change the length of an existing parameter, or add anothernon-optional parameter, create a wrapper subprocedure to make it backwardcompatible.

If you can't do that, then manually change the service program signatureso that older programs won't run until they've been recompiled. (Butavoid this if at all possible.)

A wrapper subprocedure would solve your problem quite nicely, in thiscase.


Keep the old subprocedure, but make it a wrapper. For example:

     P VT100GetControlChar...
     P                 B                   export
     D                 pi             5    varying
     D  piName                       25    value
     D retval          s              5A
      /free
        retval = VT100GetControlChar25(piName)
        return retval;
      /end-free
     P                 E

     P VT100GetControlChar25...
     P                 B                   export
     D                 pi            25    varying
     D  piName                       25    value

       .... do the real work here ....

     P                 E

Existing programs will work without being recompiled, since they stillcall VT100GetControlChar, which still only returns 5A varying.

New programs that need the extra 20 chars should callVT100GetControlChar25, since it returns the longer value.